Align the side bar on the first run by setting its width
To make Gwenview pretty the sidebar is supposed to align with a separator in the toolbar. For narrow side bar widths this is not possible because the separator is too far away from the window edge.
This commit changes it so the side bar width is set to a nice default value on the first run. Users are free to resize the side bar afterwards so it doesn't align anymore.
The first commit is the real change, the second one is me moving a method to reflect its new privateness.